Current through Register Vol. 24-06, March 15, 2024
(1) The hydrogeologic report must meet all of
the following performance standards as follows:
(a) Examine existing site conditions for
compliance with groundwater and surface water location restrictions under WAC
173-351-130,
173-351-140, and
173-351-300(7);
(b) Determine existing or background
groundwater quality conditions, including any groundwater contamination;
and
(c) Define a detection
groundwater monitoring program capable of immediate and early warning detection
for potential contamination as required in WAC
173-351-400 and the information
required in subsection (2) of this section.
(2) The hydrogeologic report contents must
include the following information:
(a) A
summary of local and regional geology and hydrology, including faults, zones of
joint concentrations, unstable slopes and subsidence areas on site; areas of
groundwater recharge and discharge; stratigraphy; erosional and depositional
environments and facies interpretation(s);
(b) A borehole program which identifies all
performance criteria of WAC
173-351-405 including lithology,
soil/bedrock types and properties, preferential groundwater flow paths or zones
of higher hydraulic conductivity, the presence of confining unit(s) and
geologic features such as fault zones, cross-cutting structures etc., and the
target hydrostratigraphic unit(s) to be monitored. The borehole program must
meet the following standards:
(i) A minimum of
twenty subsurface borings is required for MSWLF sites which are 50 acres or
less in aerial extent. For sites greater than fifty acres, twenty borings, plus
three borings for each additional ten acres thereafter, is required. Soil
borings must be established in a grid pattern with a boring in each major
geomorphic feature such as topographic divides and lowlands;
(ii) Each boring will be of sufficient depth
below the proposed grade of the bottom liner as to identify soil, bedrock and
hydrostratigraphic unit(s) conditions as required in WAC
173-351-405;
(iii) The jurisdictional health department,
with the written concurrence of the department, may approve alternate methods
including geophysical techniques, either surface or downhole including electric
logging, sonic logging, nuclear logging, seismic profiling, electromagnetic
profiling and resistivity profiling in lieu of some of the number of borings
required in the subsurface borehole program of (b)(i) of this subsection,
provided sufficient hydrogeological site characterization can be accomplished
and prior approval is obtained;
(iv) Each boring sample must be collected
from each lithologic unit and tested for all of the following:
(A) Particle size distribution by both sieve
and hydrometer analyses in accordance with approved ASTM methods (D422 and
D1120);
(B) Atterburg limits
following approved ASTM methods (D4318); and
(C) Classification under the unified soil
classification system, following ASTM standard D2487-85.
(v) Each lithologic unit on site will be
analyzed for:
(A) Moisture content, following
approved ASTM methods (D2216); and
(B) Hydraulic conductivity by an in-situ
field method or laboratory method approved by the jurisdictional health
department and the department. All samples collected for the determination of
permeability must be collected by standard ASTM procedures.
(vi) All boring logs must be
submitted with the following information:
(A)
Soil and rock descriptions and classifications;
(B) Method of sampling;
(C) Sample depth;
(D) Date of boring;
(E) Water level measurements;
(F) Soil test data;
(G) Boring location; and
(H) Standard penetration number of ASTM
standard D1586-67.
(vii)
All borings not converted to monitoring wells or piezometers must be carefully
backfilled, plugged and recorded in accordance with WAC
173-160-420;
(viii) During the borehole drilling program,
any on-site drilling and lithologic unit identification must be performed by a
geologist or other licensed professional in accordance with the requirements of
chapter 18.220 RCW, Geologists, who is trained to sample and identify soils and
bedrock lithology.
(c)
Depths to groundwater and hydrostratigraphic unit(s) including transmissive and
confining units;
(d) Potentiometric
surface elevations and contour maps; direction and rate of horizontal and
vertical groundwater flow;
(e) A
description of regional groundwater trends including vertical and horizontal
flow directions and rates;
(f) All
elevations and top of well casings must be related to the North American
vertical datum of 1988 (NAVD88) and the horizontal datum must be in accordance
with chapter 58.20 RCW, Washington Coordinate System and as amended per chapter
332-130 WAC;
(g) Quantity,
location, and construction (where available) of private and public wells within
a two thousand foot (six hundred ten meter) radius of site;
(h) Tabulation of all water rights for
groundwater and surface water within a two thousand foot (six hundred ten
meter) radius of the site;
(i)
Identification and description of all surface waters within a one-mile (1.6
kilometer) radius of the site;
(j)
A summary of all previously collected groundwater and surface water analytical
data, and for expanded facilities, identification of impacts from the existing
facility on ground and surface waters;
(k) Calculation of a site water
balance;
(l) Conceptual design of a
groundwater and surface water monitoring system, including proposed
installation methods for all devices and well construction diagrams, and where
applicable a vadose zone monitoring plan;
(m) Land use in the area, including nearby
residences;
(n) A topographic map
of the site and drainage patterns; an outline of the waste management area and
MSWLF units, property boundary, the proposed location of groundwater monitoring
wells; and
(o) Geologic
cross-sections.
(3)
Groundwater flow path analysis. The hydrogeologic report must include a summary
groundwater flow path analysis which includes all supportive documentation, and
calculations of the performance criteria of WAC
173-351-405.
Statutory Authority:
RCW
70.95.020(3),
70.95.060(1), and
70.95.260(1),
(6). 12-23-009 (Order 07-15), §
173-351-490, filed 11/8/12, effective 12/9/12. Statutory Authority:
Chapter
70.95 RCW and 40 CFR 258.
93-22-016, § 173-351-490, filed 10/26/93, effective
11/26/93.